JPH07100825A - Mixing of thermoplastic resin with additive and mixing device - Google Patents

Abstract

PURPOSE:To mix thermoplastic resin with a liquid additive efficiently and uniformly by passing a thermoplastic resin melt through a static mixer, then diverting a part thereof and mixing this diverted melt with a liquid additive using another static mixer to return the mixture to the upstream side of the first static mixer. CONSTITUTION:A resin melt is extracted from a hold tank (a) by a gear pump (b), then a part of the melt is diverted after passing it through a static mixer (c), and is extracted continuously by a gear pump (d). An additive is thermally fused in a tank (e), then is allowed to join the diverted flow of the melt by a plunger pump (f) and the diverted flow is allowed to pass through a static mixer (g). This mixture is returned to the upstream side of the static mixer (c) so that it joins a main flow and is pelletized after passing it through the static mixer (c).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for mixing a thermoplastic resin with an additive and an apparatus therefor. More specifically, by efficiently and uniformly mixing a thermoplastic resin melt with a large viscosity difference and a liquid additive, the occurrence of problems caused by poor mixing of the additives is prevented, and a high-quality thermoplastic resin composition is obtained. The present invention relates to a method and an apparatus for efficiently and stably producing lactic acid.

[0002]

2. Description of the Related Art Thermoplastic molding is performed by injection molding,
Blow molding, extrusion molding, calender molding, etc. are generally used.In this case, the slipperiness of the resin is the mold releasability in injection molding and blow molding, and the slippage of the die in extrusion molding. In the calendering, the peelability of the roll is affected, which is important. For example, in injection molding, if the slipperiness of the resin is low, the molded product will not be cracked or separated from the mold at the time of mold release, and the molding machine must be stopped after each mold opening, Productivity and workability during molding will be hindered. For this reason, in general, a method of adding and mixing a lubricant in a thermoplastic resin is adopted in order to improve these drawbacks.

These thermoplastic resins and lubricants are heated and melted and mixed in a liquid state, but the addition ratio of the lubricant is usually as small as 100 to 2,000 ppm, and the thermoplastic resin melt and liquid additives are added. Viscosity ratio of 100,000:
Since it exceeds 1, mixing a very small amount of such a large viscosity ratio requires a considerable amount of energy. However, if the mixture of the lubricants is non-uniform, sufficient lubricity cannot be obtained, and problems such as cracking at the time of mold release described above occur, or strands break during granulation, resulting in stable operation. May not be possible. Furthermore, transparent thermoplastic resins such as polystyrene resin and polymethylmethacrylate resin may cause white turbidity and significantly impair the appearance.

In addition to a lubricant, various additives are often added to a thermoplastic resin in order to impart a desired function. For example, if an aliphatic hydrocarbon is added to the thermoplastic resin, the fluidity can be improved, and if an alkylbenzotriazole is added, it acts as an ultraviolet absorber. Further, by adding a polyorganosiloxane represented by polydimethylsiloxane to the rubber-modified polystyrene resin, it is possible to improve abrasion resistance and impact strength. As described above, the types of additives added to the thermoplastic resin are diverse, and these additives are often used in combination, but similar to the case of the lubricant, the function is manifested if the mixing is not sufficient. Is not enough,
The appearance may be impaired and various operational problems may occur.

As a method of adding these additives to the thermoplastic resin, the following three methods are generally adopted. Mixing in the polymerization equipment where the thermoplastic resin is added before or during the polymerization Mixing in the single-screw or twin-screw extruder Mixing in the static mixer

In the method of adding before the start of polymerization or during the polymerization, the additives are often mixed uniformly in the resin, but when the unreacted monomers and the solvent are devolatilized, some of the additives are unreacted. It has the drawback that it evaporates together with the monomer and solvent and the yield in the resin deteriorates. In addition, depending on the type of additive, there are some that inhibit the polymerization reaction itself.

In the method using the extruder, the extruder itself is expensive and the energy required for mixing is considerably large.

The method of using the static mixer of 1 is more advantageous in terms of energy than the method of 1, but in order to obtain sufficient mixing, for example, when an SMX type static mixer of Sruzer Co. is used, as described later,
When the number of elements is 0 or less, the number of elements is increased and a considerable pressure loss is generated, which requires a large pressure generating device. Further, since the length of the mixer itself becomes very long, the unit price of the mixer becomes expensive and a large space is required for installation.

For the static mixer, see "Higihara Shingo," Static Mixer, "p.155, (19).
81) Nikkan Kogyo Shimbun Co., Ltd. ”, for a mixture having a large mixing ratio and a high viscosity ratio of two kinds of stock solutions, a part of the mainstream static mixer is partially branched to separate another static mixer. A method of premixing has been proposed, but the viscosity ratio in this case is at most 10,000.
0: 1 and 100 as intended in the present invention,
The effect is not sufficient for mixing with a high viscosity ratio of 000: 1 or more. As a countermeasure against this, it is conceivable to raise the temperature of the thermoplastic resin melt, but there is a concern that the problem of resin decomposition or discoloration may occur.

[0010]

SUMMARY OF THE INVENTION An object of the present invention is to prevent the occurrence of various problems caused by poor mixing of additives such as deterioration of product appearance, deterioration of product strength, strand breakage during granulation and the like. The present invention aims to provide a mixing method and a mixing device which can economically obtain a sufficiently mixed mixture with good yield.

[0011]

Means for Solving the Problems As a result of intensive studies for solving the above problems, the present inventors have found that in a method of mixing using a static mixer, viscosity reduction and plasticization of a thermoplastic resin melt are performed. This object has been achieved by considering effects such as approaching the solubility coefficient of liquid additives.

That is, according to the present invention, in a method of mixing a thermoplastic resin and an additive through a static mixer, a part of the main flow is taken out as a split stream from the downstream side of the static mixer A installed in the main flow pipe of the thermoplastic resin melt, The mixed flow and the liquid additive are mixed through a static mixer B installed in a distribution pipe, returned to the main stream upstream of the static mixer A, and passed through the static mixer A. Mixing of the thermoplastic resin and the additive. Is the way. In the present invention, the viscosity of the thermoplastic resin melt and the viscosity of the liquid additive are V1 (cp) and V, respectively.
When it is 2 (cp), the viscosity ratio is in the relationship of the following formula 6, and the main flow rate of the thermoplastic resin melt is F1 (m ³ /
hr), the divided flow rate is F2 (m ³ / hr), and the flow rate of the liquid additive is F3 (m ³ / hr), the flow rate ratio is expressed by the following formula 7
And the relationship of Numerical formula 8 is the method of mixing the above-mentioned thermoplastic resin and additive.

[0013]

[Equation 6]

[0014]

[Equation 7]

[0015]

[Equation 8]

Further, the present invention has a flow dividing pipe on the downstream side of the static mixer A installed in the main flow pipe of the thermoplastic resin melt, and a liquid additive pipe on the upstream side of the static mixer B installed in the flow dividing pipe. And a downstream side pipe of the static mixer B is connected to an upstream side of the static mixer A, which is a mixing device of a thermoplastic resin and an additive. Further, the inner diameter of the static mixer A is D1 (m ), The inner diameter of the static mixer B is D2 (m), the flow rate inside the static mixer A is F4 (m ³ / hr), and the flow rate inside the static mixer B is F5 (m ³ / hr), The diameter and the flow rate of the static mixer are the following Equation 9 and Equation 1
It is a mixing apparatus of the above-mentioned thermoplastic resin and additive, which has a relationship of 0.

[0017]

[Equation 9]

[0018]

[Equation 10]

The present invention will be described in detail below. Examples of the thermoplastic resin used in the present invention include ethylene resin, propylene resin, butene-1 resin, olefin resin represented by ethylene-propylene copolymer resin, styrene resin, rubber-modified styrene copolymer resin, and styrene. −
Acrylonitrile copolymer resin, methyl methacrylate-styrene copolymer resin, acrylic acid-styrene copolymer resin,
Acrylonitrile-butadiene-styrene copolymer resin,
Methyl methacrylate-butadiene-styrene copolymer resin, acrylonitrile-methyl methacrylate-butadiene-styrene copolymer resin, styrene resin represented by styrene-butadiene block copolymer resin, methyl methacrylate resin, vinyl chloride resin or its Examples of the copolymer resin include, but are not limited to, those listed here.

Next, as the additive used in the present invention,
So-called modifiers such as lubricants, plasticizers, antistatic agents, ultraviolet absorbers, stabilizers and the like, and additives for the purpose other than those described here can also be used. However, since the modifying agent often has two or more kinds of effects, the modifying effect becomes more complicated depending on the combined use.

Here, the specific examples of the additives that can be used regardless of the purpose of the reforming are aliphatic hydrocarbons,
Examples include higher fatty acids, aliphatic alcohols, fatty acid amides, metal soaps, fatty acid esters, polyorganosiloxanes, alkyl sulfonates, ethylene oxide adducts of fatty acids, hindered phenols, and benzotriazole compounds. It is not limited to the ones.

In the present invention, it is essential that these additives are liquid, and those that are liquid at room temperature can be used as they are, but those that are solid at room temperature need to be heated to be liquid. is there. If it remains solid, it is difficult to continuously supply it to the continuous flow of the molten thermoplastic resin, and the measuring equipment becomes very expensive. As a method of heating a solid substance to a liquid state at room temperature, it can be easily carried out by, for example, filling an additive in a container equipped with a heating device and heating it to a melting point or higher.

The temperature of the liquid additive may be any temperature that can maintain the liquid state, but the difference from the temperature of the thermoplastic resin melt is preferably 150 ° C. or less, more preferably 100.
Within 50 ° C, most preferably within 50 ° C. If the temperature of the liquid additive is too low, the temperature of the thermoplastic resin melt may be lowered at the inlet of the static mixer B, the viscosity may increase, and the fluidity may deteriorate. On the contrary, if the temperature of the liquid additive is too high, the thermoplastic resin may be discolored or decomposed.

The present invention will be described below with reference to FIG. 1, but the present invention is not limited thereto.

In the present invention, the amount of the additive used is such that the flow rate of the main flow F1 of the thermoplastic resin melt is F1 (m ³ / hr),
When the flow rate of the liquid additive is F3 (m ³ / hr), (F3
The value of / F1) is 0.0001 to 0.01, preferably 0.0002 to 0.00
5, more preferably 0.0005 to 0.002. (F3 /
When the value of F1) is 0.0001 or less, the effect of the additive is not exerted, and when it is 0.01 or more, the mixing into the thermoplastic resin is poor and the appearance is spoiled or the unmixed additive adheres to the die. It causes problems such as.

The type of static mixer used in the present invention is not particularly limited. For example, a right-handed twist element and a left-handed twist element manufactured by Kenix are arranged alternately and in series, a SMX static mixer manufactured by Sruzer, SMXL static mixer, SMV static mixer and SMR static mixer, Toray high mixer, Rus static mixer,
Although a static mixer manufactured by Comax Co., Ltd. can be used, it is preferable to use an SMX static mixer manufactured by Sruzer, considering the number of elements required for mixing and the required pressure loss. The static mixer A and the static mixer B may be of the same type or of different types.

The shapes of the static mixer A and the static mixer B are generally preferably cylindrical in consideration of the stagnant portion and the like, but are not limited thereto. It is desirable that the inner diameter D1 (m) of the static mixer A be within the range represented by the following formula 11 with respect to the flow rate F4 (m ³ / hr) of the fluid flowing therein.

[0028]

[Equation 11]

When the inner diameter is such that the value of (F4 / D1 ³ ) is 50 or less, the number of elements required for mixing becomes very large, and the unit price of the mixer becomes expensive.
It is not economical because it requires a large space for installation. On the other hand, conversely, in the case of the inner diameter where the value of (F4 / D1 ² ) is 2000 or more, the pressure loss becomes very large, which is not industrially practical.

Inner diameter D2 (m) of static mixer B
Is the same as for static mixer A, mixer B
It is desirable that the flow rate F5 (m ³ / hr) of the fluid flowing inside is within the range represented by the following formula 12.

[0031]

[Equation 12]

In the present invention, the location where the main stream F1 of the thermoplastic resin melt and the split stream F2 are branched must be on the downstream side of the static mixer A. It is considered that this is because the additives are already mixed in the downstream of the static mixer A, and therefore the mixing is easier due to the fact that the split stream is in a state of viscosity reduction or plasticization and the additive solubility coefficient is approached. . Also, F1 and F2
The flow rate ratio (F2 / F1) is 0.01 to 0.3, preferably 0.
The range is 03 to 0.2, and more preferably 0.05 to 0.15.
If the value of (F2 / F1) is 0.01 or less, set F2 to F
The effect of premixing with the additive by diversion from 1 is weakened, and as a result, the static mixer A becomes long, which is not preferable. On the other hand, when the value of (F2 / F1) is 0.3 or more, the required length of the static mixer B becomes long, the pressure loss becomes large, the apparatus becomes large, and the extraction pump of F2 becomes expensive. Is not preferable.

As described above, the present invention provides a method and an apparatus for efficiently mixing a thermoplastic resin melt with a liquid additive having a large viscosity difference. Part is taken out as a split stream from the downstream side of the static mixer A, the split stream and additives are mixed using another static mixer B, then returned to the main stream on the upstream side of the static mixer A, and the whole is mixed. The present invention can be applied to all fields of use of, that is, fields such as uniform dispersion of slurry and gas absorption.

[0034]

EXAMPLES The present invention will be specifically described below with reference to examples and figures, but these do not limit the scope of the present invention.

Example 1 In this example, the thermoplastic resin has a weight average molecular weight of 35.
A polystyrene resin of 0,000 was used, and stearic acid (manufactured by NOF Corporation: trade name bead stearic acid pine) was used as an additive.

The polystyrene resin is melted and plasticized by a single-screw extruder, and the thermoplastic resin melt hold tank a shown in FIG.
Was continuously fed to. The resin temperature at the extruder outlet is 240 ° C, and its melt viscosity is about 10 (sec ^-1 ) at a shear rate.
It was 4,000,000 cp. This thermoplastic resin melt hold tank a had a jacket on the outside, and the heat transfer oil having the same temperature as the temperature of the molten resin was passed through the jacket to prevent the molten resin from solidifying.

The molten resin in the thermoplastic resin melt hold tank a was extracted by the gear pump b at a rate of 100 l / hr to make it the main stream and passed through the static mixer A. On the downstream side of the static mixer A, a part of the main flow was continuously extracted by the gear pump d to make a split flow. The rotation speed of the gear pump d was adjusted so that the split flow rate was 5 l / hr.

Stearic acid as an additive was added at 95 ° C. in an additive melting tank e equipped with a steam-through jacket.
It was heated to melt and melted, and it was merged into the branched flow of the thermoplastic resin melt at a flow rate of 60 cc / hr by a plunger pump f and passed through a static mixer B. When the viscosity of the stearic acid melt at 95 ° C. was measured, it was about 5 cp. The mixture of this split stream from the static mixer B and stearic acid was supplied to the upstream side of the static mixer A and was combined with the main stream.

For the static mixer A, an SMX static mixer with an outer jacket having an inner diameter of 0.0527 m and a length of 0.527 m (10 elements) manufactured by Sruzer Co. was used. For the static mixer B, an inner jacket having an outer jacket of 0.0214 m and a length of 10 elements was used. A 0.17 m (8 element) SMX static mixer manufactured by Sruzer was used. A heating medium of 240 ° C, which is the same as the molten resin temperature, was passed through these jackets.

The mixture of the molten resin and the additive discharged from the static mixer A was taken out through a strand die h installed downstream of the static mixer A, and pelletized by a pelletizer.

Regarding the test conditions, the strands flowing out of the strand die flowed smoothly, and no troubles in the process such as strand breakage occurred even during the test time of 8 hours.

When the pellets obtained in this example were press-molded and the molded product was observed with the naked eye, no cloudiness was found in the resin. The pellets were treated with ruthenium tetroxide vapor, dyed with stearic acid, and then sliced into thin pieces, and the state of dispersion of stearic acid was confirmed with a transmission electron microscope. As shown in FIG. 2, stearic acid was finely dispersed throughout the resin. It was observed that the black portion in FIG. 2 is stearic acid and the white portion is polystyrene resin.

Further, a molded product as shown in FIG. 3 was molded with the pellets obtained in this example, and the cracks at the time of releasing from the mold were evaluated, and the results shown in Table 1 were obtained. . The molding conditions at this time were as follows. Molding machine: OKM-150 manufactured by Okuma Klaus Maffei
/ 600A Molding temperature: Cylinder temperature from under the hopper to the nozzle. 185 ° C, 195 ° C, 205 in order from the bottom of the hopper
℃, 215 ℃, 215 ℃ Mold temperature: 40 ℃ Injection time: 5 seconds Cooling time: 12 seconds Injection speed: 98% Injection pressure: 140 bar

Comparative Example 1 In Example 1, the number of rotations of the gear pump d was increased so that the split flow rate was 25 l / hr. The discharge pressure of the gear pump d was 200 kg / cm ² G, which is the design pressure of the apparatus. The test was canceled because it was almost over.

Comparative Example 2 In Example 1, the split flow was branched on the upstream side of the static mixer A, and the rotation speed of the gear pump d was adjusted so that the flow rate of the split flow was 5 l / hr. The phenomenon of strand breakage was not observed at the exit of the strand die, but the obtained pellets were examined for mold releasability of the injection-molded product in the same manner as in Examples. Was more.

Comparative Example 3 In Example 1, the test was conducted by using only the static mixer A without adopting the flow dividing method, but using the static mixer A with a length of 1.054 m (20 elements).
As a result, the phenomenon of strand breakage at the exit of the strand die was observed, and when pellets were pressed,
White turbidity was observed here and there due to poor mixing of stearic acid.

The dispersion state of stearic acid was observed in the obtained pellets by the same method as in Example 1. As shown in FIG. 4, stearic acid (the portion which appears black) was large spherical and unevenly distributed in the resin. Was confirmed.

Further, as a result of examining the mold releasability of the injection-molded article in the same manner as in Example 1, as shown in Table 1, cracking occurred at a considerable rate.

Comparative Example 4 A test was conducted in the same apparatus as in Comparative Example 3 without adding stearic acid. An injection-molded article similar to that of the example was molded with the obtained pellets, and the mold releasability was examined. As shown in Table 1, cracking occurred frequently in the resin to which stearic acid was not added.

[0050]

[Table 1]

[0051]

As described above, according to the present invention, when the static mixer is used to mix the additives in the thermoplastic resin and the additives, the viscosity of the thermoplastic resin melt and the viscosity of the additives are greatly different. Mixing can be achieved efficiently and stably, and the static mixer can be downsized. The molded product of the resin composition obtained by the present invention has an excellent appearance, improved product strength, and improved releasability from the mold, and thus the effects of the additives can be maximized.

[Brief description of drawings]

FIG. 1 is an example of a system diagram for carrying out the present invention.

2 is a dispersion state diagram of the thermoplastic resin mixture obtained in Example 1. FIG.

FIG. 3 is a perspective view of containers injection-molded using the thermoplastic resin mixtures of Examples and Comparative Examples.

4 is a dispersion state diagram of the thermoplastic resin mixture obtained in Comparative Example 3. FIG.

[Explanation of symbols]

a: Thermoplastic resin hold tank b: Extraction (gear) pump c: Static mixer A d: Extraction (gear) pump e: Liquid additive tank f: Plunger pump g: Static mixer B h: Strand die p ₁ : Thermoplastic resin melt mainstream piping p ₂ : Thermoplastic resin melt diversion piping p ₃ : Liquid additive piping

Claims (4)

[Claims] 1. A method of mixing a thermoplastic resin and an additive through a static mixer, wherein a part of the main stream is taken out as a branch stream from the downstream side of the static mixer A installed in the main stream piping of the thermoplastic resin melt, Static mixer B with liquid additive installed in the distribution pipe
A method for mixing a thermoplastic resin and an additive, characterized in that the mixture is mixed with the mixture, the mixture is returned to the main stream on the upstream side of the static mixer A, and the mixture is passed through the static mixer A. 2. When the viscosity of the thermoplastic resin melt and the viscosity of the liquid additive are V1 (cp) and V2 (cp), respectively, the viscosity ratio is in the relationship of the following mathematical formula 1, and the thermoplastic resin melt Main flow rate of the product is F1 (m ³ / hr), split flow rate is F2 (m ³ / hr), flow rate of liquid additive is F3 (m ³ / hr)
2. The method of mixing a thermoplastic resin and an additive according to claim 1, wherein the flow rate ratio is in the relationship of the following mathematical expressions 2 and 3. [Equation 1] [Equation 2] [Equation 3] 3. A diversion pipe is provided downstream of the static mixer A installed in the main flow pipe of the thermoplastic resin melt,
Addition of a thermoplastic resin characterized in that a liquid additive pipe is provided on the upstream side of the static mixer B installed in the branch pipe, and the downstream pipe of the static mixer B is connected to the upstream side of the static mixer A. Equipment for mixing things. 4. The inner diameter of the static mixer A is set to D1 (
m), the inner diameter of the static mixer B is D2 (m), and the flow rate inside the static mixer A is F4 (m ³ /
hr), the flow rate inside the static mixer B is F
The apparatus for mixing a thermoplastic resin and an additive according to claim 3, wherein the diameter and the flow rate of the static mixer satisfy the relations of the following formulas 4 and 5 when it is 5 (m ³ / hr). [Equation 4] [Equation 5]